Feeders for printers accomplish the line-by-line, step-by-step, or continuous advance of the record carriers (which consist, e.g., of paper webs). For a trouble-free operation of a printer, it is important that the beginning of the paper web be put expertly in the advance or guide elements of the feeder.
When putting the paper web on the pins of the belt fastener of a tractor, it is necessary, for example, to swing away the tractor flaps (i.e., covers) which hold the paper web on the pins. Therefore, tractor flaps are held movably in pivoting bearings.
Introduction of the paper web from the underside or backside of the printer also makes the swinging out of hinged parts by means of pivoting bearings necessary in some printer designs.
For shipping, swinging in of the hinged elements, which are swung out during operation, is advantageous to save shipping and packing space.
All of the examples given above have the disadvantage that hinged parts on printers require a considerable expenditure for pivoting bearings. An additional expenditure arises if the hinged part must further be fixed in the positions to which it is pivotable. An expenditure in this connection is hardly economically justifiable.